β-Lactones: Intermediates for Natural Product Total Synthesis and New Transformations

The exploration of b-lactone reactivity and transformations has continued since the first synthesis of these strained heterocycles by Einhorn in 1883.The principal reactivity modes of b-lactones include nucleophilic addition resulting in either acyl C2-O1 or alkyl C4-O1 cleavage, rearrangement leading to ring expansion, decarboxylation, and electrophilic reactions of b-lactone enolates.Recent advances in asymmetric b-lactone synthesis has led to further developments in the area of novel transformations of b-lactones and significantly increased applications in natural product total synthesis.The latter topic is the focus of this review and covers the period inclusive to the end of 2003. 1